Craniospinal fusion method and apparatus

ABSTRACT

An apparatus for surgical fusion of a cranio-cervical junction includes a plate member, where the plate member includes a bottom portion configured to be secured to a cranium; a top portion including a plurality of perforations extending therethrough configured to promote bone growth, wherein the top portion and the bottom portion define a graft accommodation space; and first and second side portions coupled to the top and bottom portions on first and second sides of the graft accommodation space. The first side portion is configured to receive a first support rod and the second side portion is configured to receive a second support rod.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 13/335,248, filed Dec. 22, 2011, which is a continuation ofU.S. patent application Ser. No. 11/832,646, filed Aug. 1, 2007, whichclaims the benefit of U.S. Provisional Application No. 60/887,022, filedJan. 29, 2007, all of which are incorporated herein by reference intheir entireties.

BACKGROUND

The present invention relates to a method and apparatus for fixation,stabilization and fusion of the human occipitocervical junction.

The normal range of motion of the craniospinal junction includes 27° offlexion and extension, and 90° of lateral rotation; the craniospinaljunction is thus the most mobile and articulatable part of the humanbody. It is also the most active part of the human body in movementthroughout the day, typically performing greater than 3 million motionsa year. The craniospinal junction transmits the entire nervous structureto the body (with the exception of the vagus nerve), and is thusunfortunately susceptible to a host of degenerative disorders.Emblematic of these is rheumatoid arthritis, a chronic degenerativecondition that arises in 2% of the population, causing predictablechanges in the joints and bone structure of the cervical spine, oftenincluding vertical migration of the odontoid and trauma to theligamentous structures of the craniocervical junction.

25% of rheumatoid arthritis sufferers develop atlantoaxial subluxationand 9% develop basilar invagination. Clinically these patientsinvariably experience severe neck pain and neurological deficits,including weakness and sensory loss. Untreated, patients sufferprogressive decline, losing the ability to walk. The untreated patientwith myelopathy due to compression of the spinal cord has a 50%likelihood of dying within one year. Surgical intervention is thereforenecessary to stabilize the craniocervical junction, restore neurologicfunction and prevent further neurologic deterioration. However,occipitocervical stabilization in rheumatoid arthritis can be especiallychallenging because of such factors as poor bone quality, poornutritional status and long term steroid use.

There are also other common causes of cranio-cervical instability,including traumatic fractures, which can include approximately 3,000fractures of the upper spine related to head trauma each year;congenital diseases, including Down's, Morquio's and spondyloepiphysealdysplasia syndromes, with a prevalence of at least 50,000; osteogenesisimperfecta, with a prevalence of 7,000 patients; cancer, with about 1000cases per year; and numerous causes of bone softening. Tumors andinfections may also cause destruction of the stabilizing elements.

However, the largest group of patients suffering from poorcraniocervical stabilization lies in the pediatric group amongst a largegroup of children who have been misdiagnosed with neuropsychiatricdisorders, such as Asperger's Syndrome, autism, Attention DeficitHyperactivity Disorder and forms of dyslexia who harbor underlyingdisorders of the brainstem and spinal cord which result from subtle andsometimes gross anomalies which result in mechanical deformation andabnormal stresses of the neuraxis at the craniocervical junction.Various disorders have been found to frequently result in chronic andsubtle neurological changes: retroflexion of the odontoid, platybasia,non-traditional forms of basilar invagination and an abnormalclivo-axial angle, which can result in deformity of the brainstem andupper spinal cord.

The clivioaxial angle is depicted in FIG. 1, while an example of basilarinvagination is depicted in the image that is shown in FIG. 2, withcompression to the brainstem being clearly visible. These conditionshave been reported to cause such symptoms as sleep apnea, delayedspeech, gastroesophageal reflux, and altered behavior such as attentiondeficit disorder, headaches, and a myriad of other sensori-motorsyndromes. The ubiquity of craniospinal junction pathology has onlyrecently been appreciated.

Hitherto, patients undergoing craniospinal stabilization have requiredan arduous surgery and recovery. Some patients undergo a decompressivesurgery from the front of the neck (transoral resection of the uppermostpart of the spine), followed by fusion in the back of the neck, andfollowed by three months of stabilization in a halo brace, whichencompasses the head (held by four screws in the skull) and the upperbody.

Numerous fixation devices have been described such as those that aredisclosed in U.S. Pat. Nos. 5,030,220, 5,034,011, 5,545,164, 5,507,745,6,547,790, 6,524,315, and 6,902,565; and U.S. Publication Nos.2005/0288669, 2005/0283153, and 2005/0080417, all of which are herebyincorporated by reference as if set forth fully herein.

A need exists for a system and methodology that accomplishes the goalsof reduction of deformity, successful immobilization and fusion of thecraniospinal junction, in a shortened surgery, thereby allowing thepatient to return to a normal quality of life within a short period oftime.

SUMMARY

Accordingly, it is an object of the invention to provide a system andmethodology that accomplishes the goals of reduction of deformity,successful immobilization and fusion of the craniospinal junction, in ashortened surgery, thereby allowing the patient to return to a normalquality of life within a short period of time. In order to achieve theabove and other objects of the invention, a method for effecting fusionof the human occipitocervical junction according to a first aspect ofthe invention includes steps of effecting fusion of a first portion of abone forming material based structural member to a human cranium; andeffecting fusion of a second portion of the bone forming material basedstructural member to a least one portion of a human cervical spine,whereby a fusion of the human occipitocervical junction is achieved.

An article for use in the surgical fusion of the human occipitocervicaljunction according to a second aspect of the invention includes a platemember having an outer edge, an outer surface and an inner surface thatis constructed and arranged to be secured to a human cranium, the platemember being configured so as to define a graft accommodation spacebetween the inner surface of the plate member and the cranium when theplate member has been secured to the cranium, the graft accommodationspace being defined in part by a portion of the outer edge that iselevated with respect to a portion of the inner surface that iscontacting the cranium so that the graft accommodation space is open toa space outside of the graft accommodation space, whereby a bonematerial based structural member may be positioned within the graftaccommodation space so as to be fused to the cranium and to extend awayfrom the plate member.

A system according to a third aspect of the invention for fusing a bonematerial based structural member to a human cranium includes a platemember, the plate member being constructed and arranged to securelyposition a bone material based structural member against a humancranium, the plate member having at least one threaded hole definedtherein; a rod member, the rod member having a hole defined therein; atriple screw member that is sized to fit within said hole that isdefined in the rod member, the triple screw member having a firstthreaded portion for engaging the threaded hole in the plate member, asecond threaded portion for engaging the human cranium and a thirdthreaded portion; and a nut member secured to the third threadedportion, whereby the nut member may be tightened in order to secure therod member, the plate member in the cranium and desired relativepositions so as to promote fusion of said bone material based structuralmember to the human cranium.

A system for effecting fusion of the human occipitocervical junctionaccording to a fourth aspect of the invention includes a first bonematerial based structural member that is positioned so as to facilitatefusion of a first portion thereof to a human cranium and a secondportion thereof to a cervical vertebral body; a second bone materialbased structural member that is positioned so as to facilitate fusion ofa first portion thereof to a human cranium and a second portion thereofto a cervical vertebral body; and a transverse connector that ispositioned to compress the first bone material based structural memberand the second bone material based structural member against a vertebralbody.

According to a fifth aspect of the invention, a system for effectingfusion of the human occipitocervical junction includes surgicallyimplantable instrumentation including a first support rod; a secondsupport rod; cranium attachment means for attaching respective firstportions of the first and second support rods to a human cranium;vertebral attachment means for attaching respective second portions ofthe first and second support rods to a human cervical vertebral body;and wherein the first and second support rods are contoured to ensure apostoperative craniospinal angle that is within a range of about 80° toabout 90°.

A system for effecting fusion of the human cranio-cervical junctionaccording to a sixth aspect of the invention includes surgicallyimplantable instrumentation preferably including cranium attachmentstructure for attaching to a human cranium; two appendages that areintegral with the cranium attachment structure; vertebral attachmentstructure for attaching respective second portions of the first andsecond appendages to a human cervical vertebral body; and wherein thefirst and second appendages are contoured to ensure a postoperativeclivo-axial angle of about 155° to about 165°.

Another embodiment relates to a an apparatus for surgical fusion of acranio-cervical junction, comprising a plate member comprising a bottomportion configured to be secured to a cranium; a top portion including aplurality of perforations extending therethrough configured to promotebone growth, wherein the top portion and the bottom portion define agraft accommodation space; and first and second side portions coupled tothe top and bottom portions on first and second sides of the graftaccommodation space; wherein the first side portion is configured toreceive a first support rod and the second side portion is configured toreceive a second support rod.

Another embodiment relates to a cranio-cervical fixation system,comprising a first spinal rod configured to be coupled to a vertebralbody; a second spinal rod configured to be coupled to the vertebralbody; and a plate member configured to be secured to a cranium andreceive the first and second spinal rods to provide a desired fixationof the vertebral body relative to the cranium; wherein the plate memberdefines a graft accommodation space between a top portion of the platemember and the cranium, wherein the top portion includes a plurality ofapertures formed therein and wherein the graft accommodation space isconfigured to receive bone growth material to fuse to the cranium.

Another embodiment relates to a plate member usable in a fixation systemto fuse a cranium to a vertebral body, the plate member comprising abody defining a graft accommodation space therein, the body furtherincluding a generally planar bottom surface; a generally planar rearsurface extending upward from the bottom surface; and a contoured topsurface providing a smooth contoured peripheral top of the plate memberextending from the bottom and rear surfaces.

These and various other advantages and features of novelty thatcharacterize the invention are pointed out with particularity in theclaims annexed hereto and forming a part hereof. However, for a betterunderstanding of the invention, its advantages, and the objects obtainedby its use, reference should be made to the drawings which form afurther part hereof, and to the accompanying descriptive matter, inwhich there is illustrated and described a preferred embodiment of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an image depicting the clivo-axial angle in a human, with anabnormal clivo-axial angle being shown.

FIG. 2 is an annotated image depicting compression of the brainstem as aresult of an abnormal clivo-axial angle in a human.

FIG. 3 is a fragmentary perspective view of a system for effectingfusion of the human occipitocervical junction according to a preferredembodiment of the invention.

FIG. 4 is a fragmentary cross-sectional view of a portion of the systemthat is depicted in FIG. 3.

FIG. 5 is a fragmentary cross-sectional view depicting a fasteningassembly that is constructed according to a preferred embodiment of theinvention.

FIG. 6 is a fragmentary top plan view of the fastening assembly that isdepicted in FIG. 5.

FIG. 7 is a diagrammatical depiction of a fastening tool that isdesigned to be used in conjunction with the fastening assembly that isdepicted in FIG. 5, shown in a first operative position.

FIG. 8 is a diagrammatical depiction of the fastening tool that is shownin FIG. 7, shown in a second operative position.

FIG. 9 is a fragmentary side elevational view of one component of thesystem that is depicted in FIG. 3.

FIG. 10 is a cross-sectional view depicting certain components of thesystem that is shown in FIG. 3.

FIG. 11 is a fragmentary cross-sectional view depicting certaincomponents of the portion of the system shown FIG. 3 that is depicted inFIG. 10.

FIG. 12 is a diagrammatical depiction of certain components of theportion of the system that is shown in FIG. 10.

FIG. 13 is a fragmentary perspective view of a system for effectingfusion of the human occipitocervical junction according to analternative embodiment of the invention.

FIG. 14 is a top perspective view of a plate member according to analternative embodiment.

FIG. 15 is a rear perspective view of the plate member of FIG. 14according to one embodiment.

FIG. 16 is a top view of the plate member of FIG. 14 according to oneembodiment.

FIG. 17 is a rear view of the plate member of FIG. 14 according to oneembodiment.

FIG. 18 is a bottom perspective view of the plate member of FIG. 14according to one embodiment.

DETAILED DESCRIPTION

The present invention relates to a system and method for stabilizing andfusing the human craniospinal junction. The technology is predicatedupon the importance of first, reduction of the deformity at thecraniospinal junction, and second of providing the surface areaavailable for and the mileau most conducive to formation of bone fusion.It accomplishes the latter by providing greater bone surface availablefor bone fusion, and through application of load to the graft. Thetechnology involves fewer steps to apply, therefore provides for fasterapplication, and shorter surgery with respect to conventional processes.

Referring now to the drawings, wherein like reference numerals designatecorresponding structure throughout the views, and referring inparticular to FIG. 3, a system 10 for use in the surgical fusion of thehuman occipitocervical junction according to a preferred embodiment ofthe invention includes a first bone forming material based structuralmember 12 and a second bone forming material based structural member 14.

The two bone forming material based structural members 12, 14 may bebone grafts that are harvested from another part of the patient's body,such as a rib, grafts from a cadaver, or a material that is constructedand arranged to facilitate the growth of bone. The invention isaccordingly not limited to bone, but may use bone substitutes ornon-osseous materials to accomplish long-term fixation of the cranium tothe spine. For example, the two bone forming material based structuralmembers 12, 14 may be fabricated from a metallurgically bonded porousmetal coating that is constructed and arranged to encompass and containbone graft material, such as the material that is marketed under thetrade name TRABECULAR METAL by Zimmer Inc. of Warsaw, Ind.

The two bone forming material based structural members 12, 14 couldalternatively be fabricated from a bone forming material such as a bonesubstitute that is fabricated from a collagen base and contains boneforming materials, or bone enhancing chemicals. Thus a bone formingmaterial could be embodied as a fabricated mesh that functions as a boneconductor (that a form into which bone growth would occur, or as abone-like medium such as coralline hydroxyapatite, which serves as anosteoconductor for blood vessel formation and subsequent deposition ofbone, which could be injected or poured into the space between the bonesto be fused.

Alternatively, the bone forming material could be embodied as a metallicmesh-like substance that encourages or enables bone growth, such astantalum mesh, which could be molded to fit into the space between theocciput and the spine, a bone allograft or a xenograft.

The first bone forming material based structural member 12 has a firstportion 16 that is positioned and biased against the cranial bone so asto promote bone fusion between the cranial bone and the first boneforming material based structural member 12. Accordingly, the secondbone forming material based structural member 14 has a first portion 18that is positioned and biased against the cranial bone so as to promotebone fusion between the cranial bone and the second bone formingmaterial based structural member 14. In the preferred embodiment, thesefunctions of positioning, support, biasing and promotion of fusion areeffected through the use of the unique occipital connection system 23,which will be described in greater detail below.

The bone forming material based structural members 12, 14 preferablyeach have transverse cross-sectional area of approximately 1 cm 2.

The first and second bone forming material based structural members 12,14 further respectively have second portions 20, 22 that are positionedand biased against at least one cervical vertebral body of a humancervical spine so as to promote bone fusion between the cervicalvertebral body and the respective bone forming material based structuralmember 12, 14. In the preferred embodiment, this function is effectedthrough the use of the unique vertebral connection system 100, whichwill be described in greater detail below. Preferably, the system 10facilitates a fusion between said bone forming material based structuralmembers 12, 14 and both the C1 and C2 cervical vertebral bodies.

In the preferred embodiment, the occipital connection system 23 includesa plate member 24 that is shaped so as to define an outer edge 26, anouter surface 28 and an inner surface 30, as is best shown in FIG. 4.Plate member 24 is preferably shaped to define a graft accommodationspace 32 between the plate member 24 and the cranium. The graftaccommodation space is preferably defined in part by a flange 25 definedin the plate member 24 by a portion of the plate member 24 including thecaudal portion of the outer edge 26 that is elevated away from thecranium with respect to a portion of the inner surface 30 that iscontacting the cranium so that the graft accommodation space 32 is opento a space outside of the graft accommodation space 32.

The plate member 24 is preferably a monolithic plate, composed of metal,poyetheretherketone (PEEK), bio-absorbable compound, bone or bonesubstitute. The plate member 24 preferably has a thickness of more than1 mm and less than 1 cm at the edges, and may vary in thickness. Forinstance the plate edge 26 may be 1 mm, but the central part may beincreased to 15 mm. The plate member 24 may be ovoid, rectangular,polyhedral or a composite of straight edges and curves, and thus is notconfined to a particular shape or perimeter. The plate member 24 may becoated or made of a bio-compatible material, or coated with substanceswhich are known to improve or accelerate surface attachment, or topromote bone fusion. The plate member 24 may or may not contain ametallurgically bonded porous metal coating. The plate member 24 may beslightly curved so as to be complementary to the curve of the cranium,or may be flat, or may undergo a contouring process by the surgeon orassistant at the time of surgery.

The flange 25 is an elevated contour arising from the plate member 24.The flange 25 makes available for fusion the underlying cranial surface;the elevation of the flange 25 exposes the cranial bone surface to theoverlying bone graft. The flange 25 may be constructed from the samematerial as the remainder of the plate member 24, or it may be aconstructed as a separate component that is attachable to the platemember 24. The purpose of the flange 25 is to incorporate, to enclose orto provide a fulcrum in which bone graft materials or substitutes, orother materials, may be held for the purpose of achieving a bone unionor other permanent rigid or non-rigid attachment between the cranium andthe spine.

The flange 25 may be non-perforate, or single or multiply perforate, andcould be composed of a mesh or mesh-like construction. The flange 25 ispreferably perforated to allow in-growth of bodily tissue or bloodvessels. The flange has a perforated plus non-perforated surface area ofmore than 15% of the area of the plate component.

The thickness of the flange 25 is 0.5 to 5 mm thickness. The purpose ofthe flange 25 is to entrap the bone forming substances or otherstructural members in close union with the underlying cranium, and tofacilitate in the case of bone, morphogenesis through application ofload; that is, through pressure and stabilization of the bone formingsubstances to enhance the milieu favoring new bone formation. As shownin FIGS. 3-4, flange 25 has a concave configuration adapted to form apocket with the cranium when plate member 24 is secured to the cranium.The flange 25 may have a facility to be mechanically altered in shape tofurther compress the graft.

The flange 25 will preferably rise from the plane of the portion of theplate member 24 that contacts the cranial bone for a distance that ismore than about 5 mm, to allow placement of a thickness of material thatis adequate to provide stability for growth. It is envisioned thatmalleable, or woven-bone forming substrates could be used to promotefusion, or indeed provide the scaffolding itself for fusion. Conversely,other materials could be used beneath the flange 25 to providenon-osseous, non-rigid fixation.

Flange 25 will preferably allow the passage or inset of rods, plates orother materials for connecting the cranial plate to the spine. Thepurpose of this is to lower the profile of the rod, and to minimize thepotential deformity of overlying tissue. Thus, a rod may pass through aperforation in a mesh of the flange to connect to the triple screw.Alternately, the flange may have a groove, a pop-out section or possessthe faculty of perforability to allow passage of the stabilizationelement connecting cranium to spine.

In an alternative embodiment, the flange 25 might serve to provideattachment for a non-osseous union between the cranium and spine. Theflange 25 thus may have both a physiological function and a mechanicalfunction.

Flange 25 is envisioned in the preferred embodiment to arise from thelower aspect of the plate member 24. However, alternate embodimentswould allow positioning of a single or multiple flanges in variouslocations, such as the middle, the upper or the sides of the plate. Thusthe flange should not be construed to exist only as an elevation fromthe lower edge of the plate, but, for instance, may be centered on theplate; a rim of plate could thus fully encompass the flange(s).

Whilst the preferred embodiment of the flange 25 is curved to minimizeprofile by conforming to anatomic contour, alternate forms may includebox-like constructs, or even a multiplicity of shapes and sizes thatcould be chosen for a given application, and then be secondarilyattached to the plate. For example, a low profile, curved flange couldbe applied to the plate over the cranium of an asthenic child where thethickness of skin and muscle contraindicate thickness of construct;another embodiment, for a larger person, may be a larger box-likeadaptation designed to facilitate the incorporation of a morerectanguloid, synthetic bone-forming substance or other non-osseouscompound. It is thus envisioned that a multiplicity of options toaccomplish different goals in persons (or other species of animal) ofdifferent morphology.

As is shown in FIG. 4, the first portion 18 of the second bone materialbased structural member 14 is preferably positioned within the graftaccommodation space 32 defined by the flange 25 so that the innersurface 30 of the plate member 24 is biased to provide compressivepressure against the second bone material based structural member 14.This compression will facilitate bone fusion between the second bonematerial based structural member 14 and the cranium.

As FIG. 3 shows, the first portion 16 of the first bone material basedstructural member 12 is similarly positioned within the graftaccommodation space 32 and impressively biased against the cranial boneto promote bone fusion.

Alternatively, the plate member 24 could be fabricated so as to includemore than one graft accommodation space, so that each of the twostructural members 12, 14 could be separately positioned withindifferent accommodation spaces that are defined by the inner surface 30of the plate member 24.

The inner surface 30 of the plate member 24 is preferably composed of amaterial that promotes fusion to bone. This could be accomplished bycoating the plate member 24 with anyone of a number of conventional bonegrowth promoting substances or by fabricating the plate member 24 from aporous material that is constructed and arranged to encompass andcontain bone graft material, such as the TRABECULAR METAL materialdescribed above. Plate member 24 further preferably has a plurality ofperforations 34 defined therein. Perforations 34 preferably have aminimum diameter of at least 400 microns, so as to best facilitate thegrowth of blood vessels within the newly formed bone tissue. A portion48 of the outer surface 28 of the plate member 24 may be grooved inorder to accommodate instrumentation, as will be described in greaterdetail below.

Plate member 24 preferably has a plurality of pre-drilled threadedmounting holes 36, 38, 40, 44, 46, 72 defined therein for facilitatingattachment of the plate member 24 to first portions 54, 58 of first andsecond support rods 50, 52 by means of first and second fasteningassemblies 62, 64, respectively. The plate member 24 will thereforepreferably include manifold screw holes in order to permit the supportrods 50, 52 to be secured to the plate member 24 and locations that aremost suitable for an individual patient.

A central screw hole 40 will serve to anchor a central plate screw 42.There may be multiple ‘central screw’ holes. The central screw hole(s)lie(s) approximately in the midline of the patient's body and cranium inorder to permit placement of screw(s) into the thickest part of theskull, which usually runs from the inion to the opisthion. These holesmay be threaded, partially threaded or not threaded. On each side of themidline, additional holes 38, 44, 46, 72 will be positioned to receiveadditional screws, called the triple screws 70.

The triple screws 70 engaged in the plate will serve to anchor thestabilization elements (rods, plates or other) from the cervical spine.These holes may be single or multiple; the holes may cluster, mayoverlap, may be placed in an arc, or contiguously or in separatelylocations. The holes may be placed around the edge of the flange, or onthe flat portion of the plate. These holes may be reinforced with extrathickness, and may be threaded or not. Second portions 56, 60 of thefirst and second support rods 50, 52 are secured to the cervical spineof the patient, as will be described in greater detail below.

The central plate screw 42 provides primary attachment of the plate tothe skull. It is robust, cortically threaded, of variable length,preferably having a month within a range of about 7 mm to about 12 mm.The central plate screw 42 preferably has a thickness within a range ofabout 2 mm to about 10 mm, with a blunted end. It may have a spiral lockfeature that locks the screw 42 into the plate member 24, or not. It maybe lagged to provide increased loading pressure on the plate member 24,or not. It can be made of titanium alloy, of bone, or of a bone formingor bone compatible substance. For example, a ceramic, orhydroxyl-apatite composite or metal alloy/bone composite could be used.

In an alternative embodiment, a screw/rivet could be used in lieu of thecentral plate screw 42 for rapid application. The screw or screw/rivetwould preferably have torque strength of greater than 35 inch lb andgenerate sufficient pullout strength to prevent dislodgement from thecortex. The screw or screw/rivet would be placed near the middle of theplate member 24, and be fashioned to pass through the central screw hole40 on the plate member 24.

The first and second support rods 50, 52 provide the main structuralconnection between the cranium and the upper cervical spine during theimmediate postoperative period. Support rods 50, 52 are preferablystandard titanium rods, approximately of 3-4 mm gauge, bent to conformto the correct craniospinal angle. The salient differences from otherrods currently available are two-fold. The first is an angle reflectingthe corrected reduction of the angle (α angle, FIG. 9) between thecranium and that of the spine; in the preferred embodiment this will bepre-set within a range of about 75° to about 90°. Accordingly, the firstand second support rods are contoured to ensure a postoperativecraniospinal relationship that confers a clivo-axial angle (the anglebetween the dorsum of the second cervical vertebra and the dorsum of theclivus) approaching about 145-165°, and more preferably about 155 to165°. Simultaneously, the degree of ventral brainstem compression shouldbe rendered close to zero, by virtue of the reduction of angulationbetween the cranium and spine, and in some cases by the posteriortranslation of cranium upon spine.

Second, the craniospinal support rods 50, 52 will have a pre-establishedrise option (the β rise, FIG. 9), to accommodate the non-linearity ofthe level of the posterior ring of the first cervical vertebra C1 to thesurface of the lamina of C2 and lateral mass of C3. Accordingly, thepresence of the pre-established β rise will allow the support rods 50,52 to contact the C1 and C2 laminae.

Fastening assembly 62 is shown in greater detail in FIG. 5. In thepreferred embodiment, an unthreaded hole 68 is defined in the firstportion 54 of the first support rod 50 and a threaded hole 72 isprovided in the plate member 24. Fastening assembly 62 advantageouslyincludes a unique triple screw 70 that has a first threaded portion 70at an intermediate section thereof that is sized and pitched to matewith the threaded hole 72 in the plate member 24 and a second threadedportion 76 at a lower section thereof that is constructed and arrangedto be screwed into the cranial bone 78.

Triple screws 70 have the unique characteristic of deriving stabilityfrom fixation within the skull, the plate member 24 and around the rodor plate that connects the cranium to the spine. In addition, the triplescrew 70 is tri-purposive: first, it connects the plate to the cranium;second, it connects the cranium to the craniospinal connecting devices;third, it eliminates plate torque around the central screw 42. In sodoing, it eliminates one of the steps common to all other craniospinaldevices: that of an additional and independent means of attaching theplate member 24 to the craniospinal rod or plate connector.

Triple screws 70 are so-called because they possess three functionalportions of the screw length: a threaded portion for attachment to thecranial bone 78, a threaded, or non-threaded, portion to engage theplate member 24, and a threaded portion for attaching the support rod50. The central or intermediate portion may be threaded to enhancebinding to the plate member 24, or non-threaded to allow a lag effectupon the plate member 24, in order to allow the insertion of the screwto tighten the plate down to the cranial bone 78, depending upon therequirements of the particular stabilization.

The triple screws 70 may be placed in one of many potential screw holeson each side of the plate member 24, in order to accommodate to thevariability of the system that attaches the cranium to the cervicalspine. Whilst the triple screws 70 are shown in the upper portion of theplate in the illustrated embodiment, they may in another embodiment beplaced in the lower aspect of the plate. They are not limited to beingpositioned at lateral opposite sides of the plate member 24, but may beplaced near the middle of the plate member 24. The triple screw 70 canbe turned to any direction to accommodate the craniospinal rod orconnector system.

The triple screw 70 will preferably be inserted through the plate andscrewed into the skull. The triple screw 70 will provide increasedstability to the plate and rod system by virtue of the combined fixationof the screw within the plate and the skull. The triple screw 70 may bethreaded at the level of the skull with a cortical or cancellous thread,or could in another embodiment utilize a rivet-type fixation. In anyevent, the internal portion of the screw is firmly fixated to the skull.

Triple screw 70 further includes a third threaded portion 80 at an upperportion thereof that is sized in pitch to mate with an internallythreaded hexagonal nut 82. As is shown in FIG. 6, which provides a topplan view of the fastening assembly 62, an upper surface of the triplescrew 70 is provided with a slot for receiving a screwdriver blade.

FIGS. 7 and 8 depict a unique tool 86 that is constructed and arrangedto be used in conjunction with the fastening assembly 62 and the triplescrew 70. Tool 86 includes a handle 88 and a shaft 90 that may beprovided with a universal joint 92 for accessibility purposes, e.g. toaccommodate non-orthogonal placement of the screw. For instance, ifaccess to the triple screw 70 is encumbered by a patient's corpulence,the screw may be inserted at an angle. A screwdriver blade 94 isprovided at a distal end of the shaft 90 and is preferably sized andshaped to be effectively received by the slot 84 that is defined in theupper surface of the triple screw 70. Additionally, tool 86 preferablyincludes a sleeve 96 that is slidable upwardly and downwardly on thelower portion of the shaft 90 between a first retracted position that isshown in FIG. 7 and a second, extended operative position that is shownin FIG. 8. Sleeve 96 is shaped to define an internally threaded socketthat mates with the external thread 80 of the triple screw 70. Sleeve 96is further mounted to the shaft 90 so that it is prevented from rotatingwith respect to the shaft 90. Accordingly, a surgeon may use the tool 86in the operative position that is shown in FIG. 7 in order to tightenthe triple screw 70 with respect to the plate member 24 and the cranialbone 78 with the sleeve 96 stabilizing the tool 86 with respect to thetriple screw 70 and preventing the blade 94 from slipping out of theslot 84.

Referring now to FIGS. 10-12, system 10 further includes a uniquevertical connection system 100 for positioning and biasing the secondportions 20, 22 of the first and second bone forming material basedstructural members 12, 14 against at least one cervical vertebral bodyof a human cervical spine so as to promote bone fusion between thecervical vertebral body and the respective bone forming material basedstructural member 12, 14.

In the preferred embodiment, the vertebral connection system 100includes a transverse connector 110 that is positioned to compress thefirst bone material based structural member 12 and the second bonematerial based structural member 14 against a vertebral body such as thevertebral body C2 that is depicted in FIG. 10. The transverse connector110 serves several purposes. First, the transverse connector 110 holdsthe graft material (the bone, bone substitute or other non-osseousmaterial) into close contact, and usually under pressure, with theunderlying spinal vertebrae, to facilitate in-growth of blood vessels orother tissue, as is dramatically depicted in FIGS. 10 and 11. Second,the transverse connector 110 stabilizes the two sides of the system 10,connecting the respective support rods 50, 52 from one side to that ofthe other, thereby decreasing the potential for toggling.

Accordingly, the transverse connector 110 is connected to the firststructural support rod 50 at one portion thereof that includes a firstclamping structure 112 for releasably clamping one end of the transverseconnector 110 to the first structural support rod 50. In the preferredembodiment, the first clamping structure 112 includes a curved plateportion 116 that curves about most of the circumference of a firststructural support rod 50. A screw 120 extends through first and secondholes that are defined in the curved plate portion 116 for tighteningand loosening the first clamping mechanism 112 with respect to the firststructural support rod 50.

Likewise, the transverse connector 110 is connected to the secondstructural support rod 52 at a second portion thereof that includes asecond clamping mechanism 114 for releasably clamping a second, oppositeend of the transverse connector 110 to the second structural support rod52. The second clamping structure 114 includes a curved plate portion118 that curves about most of the circumference of the second structuralsupport rod 52. A screw 122 extends through first and second holes thatare defined in the curved plate portion 118.

The curved plate portions 116, 118 of the respective clamping mechanisms112, 114 preferably extend around the circumference of the respectivesupport rod 50, 52 as viewed in transverse cross-section for an angulardistance of at least three radians. In addition, the clamping screws120, 122 are preferably positioned on the medial side of the respectivesupport rod 50, 52.

The transverse connector 110 is preferably curved so as to be concave ona side thereof that is positioned to contact the first bone materialbased structural member 12 and said second bone based structural member14.

The transverse connector 110 further preferably includes structure forpermitting adjustment of a length of the transverse connector 110,whereby a lateral spacing distance between said first and secondlaterally spaced structural support rods may be adjusted. In thepreferred embodiment, this is accomplished by constructing thetransverse connector 110 out of two separate components that areattachable to each other, specifically a first curved connector portion124 and a second curved connector portion 126, as is best shown in FIG.12.

The first connector portion 124 has a plurality of adjustment holes 130defined therein while the second connector portion 126 similarly has aplurality of adjustment holes 132 defined therein. A top-loading screwmember 128, which is best shown in FIG. 10, is provided for securing thefirst connector portion 124 to the second connector portion 126 and ispreferably applied centrally in a precise manner in order to stabilizethe first and second connector portions 124, 126. Screw member 128 ispreferably although not necessarily a lock screw having a snap off head.A Vernier scale option may be used to generate the best precise fit, butother adaptations may be used, with the most important requirement beingthat a secure fit is created.

The graft loading transverse connector component arms 124, 126 arepreferably curved, and may possess a plurality of curve sizes toaccommodate the specific graft or implanted material size. In onepossible alternative embodiment, the transverse connector arms arestraight with a rise to accommodate the underlying material.

The surgically implantable instrumentation of the system 10 that hasbeen described above, including the plate member 24 the support rods 50,52 and the transverse connector 110 may alternatively be fabricated froma bioabsorbable material that progressively loses its strength and massover time as it is absorbed into the human body. The ideal bioabsorbablematerial would have a composition that would retain sufficient strengthfor a sufficient period of time for adequate bone fusion and bone massto develop so that the first and second bone forming material basedstructural members 12, 14 would provide adequate structural strength tomaintain the fusion of the human occipitocervical junction at all timesand under all foreseeable circumstances.

Referring now to FIG. 13, a system 140 that is constructed according toan alternative embodiment of the invention includes an integratedfixation member 142 having a plate portion 144 and first and secondappendages 146, 148 that are integral and preferably unitary with theplate portion 144. The appendages 146, 148 would intimately relate tothe posterior ring of C1 (the first vertebra and the lateral mass of C2,C3 and to any of the lower vertebrae, even as low as the thoracicvertebrae The goal of the monolithic design would be to simplify andincrease the efficiency of application and stabilization of the deviceto the craniospinal junction.

Plate portion 144 is preferably constructed identically to the plateportion described above with reference to the previously describedembodiment except as is described otherwise herein. The first and secondappendages 146, 148 are preferably rigid and in the preferred embodimentare fabricated from a pair of generally parallel extending rod members150, 152. Appendages 146, 148 are preferably preformed as describedabove with reference to the first embodiment of the invention so as tobe bent at an angle reflecting the corrected reduction of the angle (αangle, FIG. 9) between the cranium and that of the spine, which in thepreferred embodiment this will be pre-set within a range of about 75° toabout 90°. Accordingly, the first and second integrated appendages 146,148 are contoured to ensure a postoperative craniospinal relationshipthat confers a clivo-axial angle (the angle between the dorsum of thesecond cervical vertebra and the dorsum of the clivus) approaching about155-165° and more preferably about 155-165°. Simultaneously, the degreeof ventral brainstem compression should be rendered zero, by virtue ofthe reduction of angulation between the cranium and spine, and in somecases by the posterior translation of cranium upon spine.

In addition, the integrated appendages 146, 148 preferably incorporate apre-established rise option (the β rise, described above with referenceto FIG. 9), to accommodate the non-linearity of the level of theposterior ring of the first cervical vertebra C1 to the surface of thelamina of C2 and lateral mass of C3. The presence of the pre-establishedβ rise will allow the integrated appendages 146, 148 to contact the C1and C2 laminae, as shown in FIG. 13.

Another advantageous feature of the embodiment of the invention that isdepicted in FIG. 13 is the provision of adjustment slots 156, 158 in thefirst and second appendages 146, 148, respectively, to permit positionaladjustment of the integrated fixation member 142 with respect to thepedicle screws 102, 104 that are used to secure the first and secondappendages 146, 148, respectively, to the C2 vertebrae. As FIG. 13shows, adjustment slot 158 as well as adjustment slot 156 may include aplurality of prepositioned apertures or adjustment holes 160, 162 topermit indexing of the pedicle screw 104 within the appendage 148 orvariability of screw purchase.

Likewise, adjustment slots 154 may be provided in the respectiveportions of the first and second appendages 146, 148 that areconstructed and arranged to be secured to the C1 vertebrae by pediclescrews 106, 108. This portion of the appendages 146, 148 is preferablyconstructed so as to be slightly flared at the C1 vertebrae to allowlateral variability.

As may be visualized from viewing FIG. 13, several possibilities oflatitude are offered for the screw heads at C1, and several options forthe screw heads of C2 are also available. The appendages 146, 148 may besolid, tubular, porous or even a metallurgically bonded porous metalcoating that is constructed and arranged to encompass and contain bonegraft material, such as the material that is marketed under the tradename TRABECULAR METAL by Zimmer Inc. of Warsaw, Ind.

A method for achieving occipitocervical fusion according to a preferredembodiment of the invention will now be described. The patient is firstpositioned prone with a Mayfield pin headrest in an appropriate sterilesurgical environment. The posterior cranium (subocciput) will then besurgically exposed.

The suboccipital bone will then preferably be lightly drilled orsculpted in order to create a flat and even surface for the positioningof the plate member 24. The plate member 24 will then be aligned withthe long axis of the patient's body and will be positioned symmetricallyabout the midline axis, so that the central screw hole 40 is preferablybisected by the midline axis of the patient's cranium as viewed in rearelevation. The center of the central screw hole 40 will then be markedon the cranium, and the plate member 24 will be removed.

A central hole will then be surgically drilled in the cranium,preferably to a depth of 5-10 mm. using a high speed drill, then by aconventional surgical hand drill to complete the drilling, preferably toa total depth of between about 8 mm to about 12 mm. The screw hole willbe tapped to a depth that is about 1 mm. longer than the screw to beused. (For example, for a 10 mm screw, tap to 11 mm depth). The platemember 24 will then be repositioned on the midline.

The central cortical screw 42 will then be inserted into the tapped holeand tightened, lagging down the plate member 24 to achieve solidfixation.

The left C1 and C2 screws 102, 106 will then be respectively insertedinto the C1 and C2 vertebral bodies as is best shown in FIGS. 3 and 10.

The left pre-contoured support rod 50 is loosely positioned within thefirst clamping mechanism on 12 of the transverse connector 110 and issecured to the left C1 and C2 screws 102, 106.

The triple screw position for the first fastening assembly 62 that bestaligns with the pre-contoured occipito-cervical rod 50 is then selected.The triple screw purchase selected is then drilled in the cranium. Thelateral screw purchase may then be tapped if it is not beenpre-threaded. The triple screw 70 is inserted.

The same operation is performed, again choosing the most appropriateposition for the triple screw for the second fastening assembly 64.

The Mayfield headholder is then released, and an open reduction of thecraniocervical junction is performed under fluoroscopy and under directinspection. It is ensured that the abnormal angulation (kyphosis) of thecraniospinal angle, and any abnormal translation of the skull isreduced, and that there is no rotation or lateral bending and nosubluxation at lower spinal levels. The head-holder is then relocked.

The clivioaxial angle is then measured with the goal of achieving anoptimal clivioaxial angle of 150° to 165°.

The support rods 50, 52 are then placed into the triple screws 70 withinthe respective fastening assembly 62, 64 and the hex nuts 82 are placedover the screws 70 and tightened.

The exposed suboccipital bone, the posterior ring of C1 and the laminaand facet joints of C2 are then surgically decorticated.

The first portions 16, 18 of the first and second bone forming materialbased structural member 12, 14 are then inserted into the graftaccommodation space 32 that is defined between the plate member 24 andthe cranium, as is best shown in FIG. 4. The cephalad part of the boneforming material based structural member should be fashioned to fitprecisely and under pressure beneath the flange 25 of the plate member24. In some embodiments, the caudal edge 26 of the plate member 24 maynow be bent down towards the cranium to further compress the graft. Thecaudal end of the graft should lie on the decorticated C1 and C2 (andlower levels where indicated) dorsal elements.

The graft loading transverse connector is then positioned to hold down,under pressure, the portions of the first and second bone formingmaterial based structural members 12, 14 that are positioned over andagainst the C1 and C2 dorsal elements. This is best illustrated in FIGS.10 and 11.

The locking screws 120, 122 are then tightened on the transverseconnector.

Demineralized bone matrix may then be applied to the fusion areas andmore cancellous bone may be applied to complete the fusion. A layeredwound closure is then performed conventionally over a drain.

A method according to an alternative embodiment of the invention wouldutilize the integrated fixation member 142 that is depicted in FIG. 13.In this method, the preferred steps are preferably slightly reordered.First, placement of the screws into the lateral mass or ring or C1 andinto the lateral mass or pedicle of C2, or into the lateral masses ofthe lower cervical or thoracic vertebrae would be performed.

Second the monolithic construct including the plate portion 144 and theintegrated appendages 146, 148, which are surrogates for the rods 56 and58 described with reference to the first embodiment of the invention, isapplied over the screw heads.

Third, the craniospinal reduction is performed.

Fourth, the plate portion 144 is screwed to the skull 23 with thecentral screw 42. The top loading nuts 106, 108 are then tightened downover the screw heads of the vertebral screws.

In all other respects, this method is identical to the method firstdescribed above.

Referring now to FIGS. 14-18, in some embodiments, system 10 isimplemented using a plate member such as plate member 224 in place ofplate member 24. In one embodiment, the implementation of system 10 isotherwise as discussed above, such that all features of system 10 asused with plate member 24 are equally applicable to plate member 224except as otherwise noted herein.

As shown in FIGS. 14-18, in one embodiment plate member 224 (e.g., anoccipital plate or member, a skull plate or member, etc.) includes a topportion 225 (e.g., a flange, etc.), a bottom portion 226, a first sideportion 228, a second side portion 230, and a front portion 231.Portions 224, 225, 226, 228, 230 and 231 may be formed as a singleunitary plate member (e.g., via a molding, casting, machining, or otheroperation), or alternatively, may be one or more separate componentsthat are subsequently joined or coupled together (e.g., using fasteners,adhesives, welding operations, etc.).

In one embodiment, top portion 225 includes a number of perforations 244(e.g., bone growth apertures, etc.) across a portion of top portion 225.As shown in FIGS. 14-18, top portion 225 extends between first andsecond side portions 228, 230 to define a graft accommodation space 232.In one embodiment, top portion 225 defines a top aperture 234 and arecess or cutout 236, which are configured to provide tool access tounderlying fasteners and components. Perforations 244 are provided abovegraft accommodation space 232 and provide communication between graftaccommodation space 232 and the environment around plate member 224.

In one embodiment, bottom portion 226 includes a number of fastenerbores 238 configured to enable fastening of plate member 224 to thecranium. As shown in FIG. 17, in one embodiment, bottom portion 226includes five fastener bores 238, with three bores extending in agenerally transversely aligned fashion across bottom portion 226 andadditional bores 238 offset forwardly and rearwardly. In someembodiments, one or more bores 238 may be provided on a removable tabportion 254 of bottom portion 226 such that if desired, the tab portionsmay be removed prior to or during a procedure. As shown in FIG. 15, inone embodiment, tab portions 254 may be formed by a weakened area 256(e.g., an area of reduced material thickness, etc.) of bottom portion226. It should be understood that according to various alternativeembodiments, the number, location, and spacing of fastener bores 238 maybe varied.

As shown in FIGS. 14-18, plate member 224 includes bottom surface 248and rear surface 250 extending upward from bottom surface 248 in agenerally perpendicular fashion. Bottom peripheral edge 252 extendsabout the front and side portions of bottom surface 248. Top surface 246in one embodiment forms a generally smooth, contoured peripheral surfaceextending between bottom peripheral edge 252 and rear surface 250.Providing a smooth top surface may avoid undesirable ridges, corners,etc. from being perceptible by a patient or others (e.g., by sight, bytouch, etc.).

Top portion 225 is an elevated contoured portion arising from the sideand front portions of plate member 224. Top portion 225 makes availablefor fusion the underlying cranial surface. The elevation of top portion225 exposes the cranial bone surface to the overlying bone graft. Topportion 225 may be constructed from the same material as the remainderof plate member 224, or it may be a constructed as a separate componentthat is attachable to plate member 224. One purpose of top portion 225is to incorporate, to enclose or to provide a fulcrum in which bonegraft materials or substitutes, or other materials, may be held for thepurpose of achieving a bone union or other permanent rigid or non-rigidattachment between the cranium and the spine.

Top portion 225 may be non-perforate, or single or multiply perforate,and could be composed of a mesh or mesh-like construction. Top portion225 is in some embodiments perforated to allow in-growth of bodilytissue or blood vessels. Top portion 225 entraps bone forming substancesor other structural members in close union with the underlying cranium,and facilitates, in the case of bone, morphogenesis through applicationof load; that is, through pressure and stabilization of the bone formingsubstances to enhance the milieu favoring new bone formation. As shownin FIGS. 14-18, top portion 225 has a concave configuration adapted toform a pocket with the cranium and bottom portion 226 when plate member224 is secured to the cranium. In some embodiments, top portion 225 orother components of plate member 224 are compressible to further providea load on bone growth or other materials.

Plate member 224 includes a number of screw bores 240 and rod bores 242.Rod bores 242 are configured to receive spinal rods 50, 52 or similarstructural components to provide a desired fixation of the craniumrelative to the spine. Screw bores 240 receive screws 241 (e.g., setscrews, etc.) to secure spinal rods 50, 52 in position within rod bores242. In one embodiment, bores 242 extend through plate member 224. Inother embodiments, rod bores 242 extend to prescribed depth within platemember 224. Screw bores 240 at least partially intersect rod bores 242such that screws 241 engage spinal rods 50, 52.

As noted above, in some embodiments plate member 224 is a monolithicplate, composed of metal, poyetheretherketone (PEEK), bio-absorbablecompound, bone or bone substitute. The various portions of plate member224 may vary in thickness. Plate member 224 is not confined to aparticular shape or perimeter, and may be coated or made of abio-compatible material, or coated with substances which are known toimprove or accelerate surface attachment, or to promote bone fusion. Insome embodiments, plate member 224 contains a metallurgically bondedporous metal coating. As discussed in further detail below, variousportions of plate member 24 may be curved so as to be complementary tothe curve of the cranium or other anatomical features, or may be flat,or may undergo a contouring process by the surgeon or assistant at thetime of surgery.

Alternatively, plate member 224 could be fabricated so as to includemore than one graft accommodation space, so that each of the twostructural members 12, 14 could be separately positioned withindifferent accommodation spaces that are defined by the inner surface ofplate member 224.

The inner surface of plate member 224 is in some embodiments composed ofa material that promotes fusion to bone. This could be accomplished bycoating plate member 224 with any one of a number of conventional bonegrowth promoting substances or by fabricating plate member 224 from aporous material that is constructed and arranged to encompass andcontain bone graft material, such as the TRABECULAR METAL materialdescribed above.

First and second support rods 50, 52 provide the main structuralconnection between the cranium and the upper cervical spine during theimmediate postoperative period. Support rods 50, 52 are in oneembodiment standard titanium rods, approximately of 3-4 mm gauge, bentto conform to the correct craniospinal angle. The salient differencesfrom other rods currently available are two-fold. The first is an anglereflecting the corrected reduction of the angle (α angle, FIG. 9)between the cranium and that of the spine; in one embodiment this willbe pre-set within a range of about 75° to about 90°. Accordingly, thefirst and second support rods are contoured to ensure a postoperativecraniospinal relationship that confers a clivo-axial angle (the anglebetween the dorsum of the second cervical vertebra and the dorsum of theclivus) approaching about 145-165°, and more preferably about 155 to165°. Simultaneously, the degree of ventral brainstem compression shouldbe rendered close to zero, by virtue of the reduction of angulationbetween the cranium and spine, and in some cases by the posteriortranslation of the cranium upon the spine.

Second, the craniospinal support rods 50, 52 may have a pre-establishedrise option (the β rise, FIG. 9), to accommodate the non-linearity ofthe level of the posterior ring of the first cervical vertebra C1 to thesurface of the lamina of C2 and lateral mass of C3. Accordingly, thepresence of the pre-established β rise will allow the support rods 50,52 to contact the C1 and C2 laminae.

The surgically implantable instrumentation of the system 10 that hasbeen described above, including the plate members 24 and 224, thesupport rods 50, 52, and the transverse connector 110, may alternativelybe fabricated from a bioabsorbable material that progressively loses itsstrength and mass over time as it is absorbed into the human body. Theideal bioabsorbable material would have a composition that would retainsufficient strength for a sufficient period of time for adequate bonefusion and bone mass to develop so that the first and second boneforming material based structural members 12, 14 would provide adequatestructural strength to maintain the fusion of the human occipitocervicaljunction at all times and under all foreseeable circumstances.

It is to be understood, however, that even though numerouscharacteristics and advantages of the present invention have been setforth in the foregoing description, together with details of thestructure and function of the invention, the disclosure is illustrativeonly, and changes may be made in detail, especially in matters of shape,size and arrangement of parts within the principles of the invention tothe full extent indicated by the broad general meaning of the terms inwhich the appended claims are expressed.

What is claimed is:
 1. An apparatus for surgical fusion of acranio-cervical junction, comprising: a plate member comprising: abottom portion configured to be secured to a cranium; a top portionincluding a plurality of perforations extending therethrough configuredto promote bone growth, wherein the top portion and the bottom portiondefine a graft accommodation space; and first and second side portionscoupled to the top and bottom portions on first and second sides of thegraft accommodation space; wherein the first side portion is configuredto receive a first support rod and the second side portion is configuredto receive a second support rod.
 2. The apparatus of claim 1, wherein atop surface of the plate member defines a generally smooth contoured topperipheral surface extending from a bottom peripheral edge of the platemember.
 3. The apparatus of claim 2, wherein the generally smoothcontoured peripheral surface is convex between opposing side edges ofthe bottom peripheral edge and between a front of the bottom peripheraledge and a rear surface of the plate member.
 4. The apparatus of claim3, wherein the bottom portion defines a generally planar bottom surfaceand wherein the rear surface defines a generally planar rear surface. 5.The apparatus of claim 1, wherein the bottom portion defines a bottomplate including a plurality of fastener apertures, wherein at least oneof the fastener apertures is provided on a removable tab portion of thebottom plate.
 6. The apparatus of claim 5, wherein the plate memberdefines at least one access aperture in a top surface of the platemember configured to enable access to fasteners received in theplurality of fastener apertures.
 7. The apparatus of claim 1, whereinthe first side portion defines a first rod bore configured to receivethe first support rod and the second side portion defines a second rodbore configured to receive the second support rod, and wherein the firstside portion is further configured to receive a first screw to engagethe first support rod within the first rod bore, and wherein the secondside portion is further configured to receive a second screw to engagethe second support rod within the second rod bore.
 8. The apparatus ofclaim 1, wherein the graft accommodation space is defined by a concavesurface extending along the inner surfaces of the first and second sideportions and the top portion.
 9. The apparatus of claim 1, wherein asurface of the plate member comprises a metallurgically bonded porousmetal coating that is configured to encompass and contain bone graftmaterial.
 10. The apparatus of claim 1, further comprising: the firstsupport rod; the second support rod; and a transverse connectorconfigured to compress a bone material based member against a cervicalvertebral body, wherein the transverse connector is configured to beattached to the first and second support rods.
 11. The apparatus ofclaim 10, further comprising the bone material based member, wherein thebone material based member is configured and positioned so as tofacilitate fusion of a first portion thereof to the cranium and a secondportion thereof to the cervical vertebral body.
 12. A cranio-cervicalfixation system, comprising: a first spinal rod configured to be coupledto a vertebral body; a second spinal rod configured to be coupled to thevertebral body; and a plate member configured to be secured to a craniumand receive the first and second spinal rods to provide a desiredfixation of the vertebral body relative to the cranium; wherein theplate member defines a graft accommodation space between a top portionof the plate member and the cranium, wherein the top portion includes aplurality of apertures formed therein and wherein the graftaccommodation space is configured to receive bone growth material tofuse to the cranium.
 13. The system of claim 12, wherein the platemember includes: a bottom portion configured to be secured to thecranium, wherein the top portion and the bottom portion define the graftaccommodation space; and first and second side portions coupled to thetop and bottom portions on first and second sides of the graftaccommodation space, wherein the first side portion is configured toreceive the first spinal rod and the second side portion is configuredto receive the second spinal rod.
 14. The system of claim 12, wherein atop surface of the plate member defines a generally smooth contoured topperipheral surface extending from a bottom peripheral edge of the platemember, wherein the generally smooth contoured peripheral surface isconvex between opposing side edges of the bottom peripheral edge andbetween a front of the bottom peripheral edge and a rear surface of theplate member, and wherein the bottom portion defines a generally planarbottom surface and wherein the rear surface defines a generally planarrear surface.
 15. The system of claim 12, wherein a bottom portion ofthe plate member defines a bottom plate including a plurality offastener apertures, wherein at least one of the fastener apertures isprovided on a removable tab portion of the bottom plate; and wherein theplate member defines at least one access aperture in a top surface ofthe plate member configured to enable access to fasteners received inthe plurality of fastener apertures.
 16. The system of claim 12, whereinthe graft accommodation space is defined by a concave surface extendingalong the inner surfaces of the first and second side portions and thetop portion.
 17. The system of claim 12, further comprising a transverseconnector configured to compress a bone material based member againstthe vertebral body, wherein the transverse connector is configured to beattached to the first and second spinal rods.
 18. A plate member usablein a fixation system to fuse a cranium to a vertebral body, the platemember comprising: a body defining a graft accommodation space therein,the body further including: a generally planar bottom surface; agenerally planar rear surface extending upward from the bottom surface;and a contoured top surface providing a smooth contoured peripheral topof the plate member extending from the bottom and rear surfaces.
 19. Theplate member of claim 18, further comprising a bottom portion definingthe generally planar bottom surface, wherein the bottom portion includesa plurality of removable tab portions, each tab portion defining anaperture therethrough configured to receive a fastener for securing theplate member to the cranium.
 20. The plate member of claim 18, furthercomprising a top portion defining at least a portion of the top surface,wherein the top portion further defines a plurality of aperturesextending therethrough and covering an area extending above the graftaccommodation space.